APC – Alternative PHP Cache

A PHP-accelerator is a PHP extension designed to improve the performance of software applications written in the PHP language.

Most PHP accelerators work by caching the compiled p-code (portable code) of PHP-Scripts to avoid the overhead of reparsing and recompiling source code on each request made for example by a stupid bot.

APC is free, open source framework that optimizes PHP intermediate code and caches data and compiled code from the PHP bytecode compiler in shared memory. APC is quickly becoming the de-facto standard PHP caching mechanism as it will be included built-in to the core of PHP starting with PHP 6